Photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO 2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed to overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability.

Methylammonium lead iodide (CH3NH3PbI3, MAPbI3) belongs to the group of organic–inorganic halide perovskites (OIHPs) that exhibit exceptional electrical and optical behavior suitable for photovoltaic applications. However, improving its structural and chemical stability and robustness remains a challenge for OIHPs to be considered a feasible active material in optoelectronic devices. This is due to the fact that this material is very susceptible to degrade under various intrinsic and extrinsic factors. Therefore, it is crucial to understand the mechanisms through which MAPbI3 undergoes chemical degradation under operating conditions such as a relatively humid environment. We present the structural characteristics of MAPbI3 under working conditions that suggest the routes of phase segregation as a result of exposing to highly moist media. We use dark pulse discharge behavior and current–voltage (I–V) variations of MAPbI3 under different moisture levels to investigate the nature of structural degradation in OIHPs. We show that while relatively lower levels of humidity (∼60% RH) have a limited impact on the structural stability of MAPbI3, exposure to higher levels of moisture (∼100% RH) results in the formation of PbI2 and aqueous CH3NH3I, which fundamentally change the charge transport characteristics in MAPbI3. Our findings explain the ongoing debate on the presence of a threshold for the humidity that triggers irreversible structural transformation and leads to full degradation of MAPbI3.

The photoreduction of CO 2 by using enzyme-mimicking polymeric metallofoldamers containing Ni-thiolate cofactors was explored. Metallofoldamers consisting of folded polymers incorporated with Ni-thiolate complexes were prepared by intramolecular Ni-thiolate coordination with thiol-functionalized linear copolymers. The folded polymer backbonem ay resemble the protein framework to provide as econd coordination environment to the active sites. We showedt hat Ni-metallofoldamers were superiorlya ctive and selective for CO 2 photoreduction. At 80 8C, the turnover frequency of the Ni-metallofoldamersc ould reach 0.69 s À1 ,w hich corresponds to 2500 turnovers per hour per Ni site. Our findings are expected to provide useful guidelines to investigate artificial enzymes and to understand the role of protein frameworks in photosynthesis.New catalytic materials that can effectively capture and sustainably convert CO 2 into carbon-based fuels are of great interest. [1] In nature, an umber of metalloenzymes [e.g.,c arbon monoxide dehydrogenase (CODH) and formate dehydrogenase] are known to be highly active for variousconversion pathways in the biological metabolism of CO 2 . [2] All of these metalloenzymes contain metal-thiolates as cofactors. [1g] For example, the CODH isolated from the anaerobic bacterium Carboxydothermus hydrogenoformans can catalyze thermodynamically reversible conversionsb etween CO 2 and CO at ac omplexN i-, Fe-, and S-containing metal-thiolate site, namely,t he [Ni-Fe 4 S 4 ] Cc luster. [3] The enzymatic conversion of CO 2 has advantages, for example, high binding affinity,e xcellent product selectivity, and minimum energy input. Inspired by metalloenzymes, considerable effort has been made to synthesize mimics that can catalyzea nalogoust ransformations found in naturals ystems. [4] However,t he overall efficiency of artificial photosynthetic sys- [a] Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.

No abstract

We report microwave assisted synthesis of a series of highly hydrophobic porous organic polymers of poly divinylbenzene (PDVB), for the first time, which were modified by amine-rich co-monomers of vinyl imidazole (VI) and vinyl triazole (VT) resulting in PDVB-VI and PDVB-VT adsorbents. There is an optimum amount of incorporated co-monomer and initiator which led to high adsorptive activity of the material towards CO2. Atmospheric CO2 adsorption was enhanced by the addition of amine moieties while maintaining an optimum surface area and pore volume. A certain amount of initiator led to better incorporation of VT monomer while surface area and pores remain accessible. A maximum CO2 adsorption of 2.65 mmolg-1 at 273 K/1 bar was achieved for triazole based adsorbent (PDVB-VT) with 0.7 g of VT and 0.07 g of initiator. In comparison with a non-functionalized material (PDVB) with 1.2 mmolg-1 CO2 uptake, the adsorption efficiency was enhanced more than twice. The adsorbent maintained its efficiency up to seven cycles. Theoretical modeling confirms the active site is nitrogen on the imidazole/ triazole ring and that incorporation of VT to the polymeric networks enhanced the adsorptive properties better than vinyl imidazole (VI) due to more active sites.While absorption by amine-solution has drawbacks of corrosion, considerable energy loss, and inefficient regeneration, this has been the most widely adopted strategy [9]. Adsorption by solids provides some Porous polymers provide several advantages of (i) clear design of the high surface area and well-defined porosity, (ii) easy processing, (iii)and light elemental composition which provide weight advantages [53]. Recently, several porous polymers (mesoporous or microporous) have been developed for CO 2 capture [54,55]. Amine modified porous polymers have also been drawn up to adsorb CO 2 more